Jörgen Bruhn

Combined EEG-fNIRS Decoding of Motor Attempt and Imagery for Brain Switch Control: An Offline Study in Patients With Tetraplegia

Combining electrophysiological and hemodynamic features is a novel approach for improving current performance of brain switches based on sensorimotor rhythms (SMR). This study was conducted with a dual purpose: to test the feasibility of using a combined electroencephalogram/functional near-infrared spectroscopy (EEG-fNIRS) SMR-based brain switch in patients with tetraplegia, and to examine the performance difference between motor imagery and motor attempt for this user group. A general improvement was found when using both EEG and fNIRS features for classification as compared to using the single-modality EEG classifier, with average classification rates of 79% for attempted movement and 70% for imagined movement. For the control group, rates of 87% and 79% were obtained, respectively, where the “attempted movement” condition was replaced with “actual movement.” A combined EEG-fNIRS system might be especially beneficial for users who lack sufficient control of current EEG-based brain switches. The average classification performance in the patient group for attempted movement was significantly higher than for imagined movement using the EEG-only as well as the combined classifier, arguing for the case of a paradigm shift in current brain switch research.

Correlation Among Ultrasound, Cross-Sectional Anatomy, and Histology of the Sciatic Nerve: A Review

Background and Objectives: Efficient identification of the sciatic nerve (SN) requires a thorough knowledge of its topography in relation to the surrounding structures. Anatomic cross sections in similar oblique planes as observed during SN ultrasonography are lacking. A survey of sonoanatomy matched with ultrasound views of the major SN block sites will be helpful in pattern recognition, especially when combined with images that show the internal architecture of the nerve. Methods: From 1 cadaver, consecutive parts of the upper leg corresponding to the 4 major blocks sites were sectioned and deeply frozen. Using cryomicrotomy, consecutive transverse sections were acquired and photographed at 78-&mgr;m intervals, along with histologic sections at 5-mm intervals. Multiplanar reformatting was done to reconstruct the optimal planes for an accurate comparison of ultrasonography and gross anatomy. The anatomic and histologic images were matched with ultrasound images that were obtained from 2 healthy volunteers. Results: By simulating the exact position and angulation as in the ultrasonographic images, detailed anatomic overviews of SN and adjacent structures were reconstructed in the gluteal, subgluteal, midfemoral, and popliteal regions. Throughout its trajectory, SN contains numerous fascicles with connective and adipose tissues. Conclusions: In this study, we provide an optimal matching between histology, anatomic cross sections, and short-axis ultrasound images of SN. Reconstructing ultrasonographic planes with this high-resolution digitized anatomy not only enables an overview but also shows detailed views of the architecture of internal SN. The undulating course of the nerve fascicles within SN may explain its varying echogenic appearance during probe manipulation.

Ultrasound-guided proximal and distal sciatic nerve blocks in children.

STUDY OBJECTIVE To present the use of ultrasonography for the performance of proximal subgluteal and distal sciatic nerve blocks in children. DESIGN Prospective descriptive study. SETTING University hospital. PATIENTS 45 ASA physical status I, II, and III patients, aged between 8 months and 16 years, scheduled for lower limb surgery. INTERVENTIONS During general anesthesia, proximal, subgluteal, and distal sciatic nerve blocks using ultrasonography were performed. If severe postoperative pain was expected, a catheter technique was used. MEASUREMENTS The injected amount of local anesthetic was noted. Based on the spread of local anesthetic, prediction for successful block was made. Complications, adverse effects, postoperative pain scores, and parent satisfaction scores were noted. MAIN RESULTS 21 proximal sciatic nerve blocks (12 single-injection and 9 continuous blocks) and 35 distal sciatic nerve blocks (17 single-injection, 6 bilateral single-injection, 4 continuous, and one bilateral continuous block) were performed. A mean initial dose of 0.25 mL.kg(-1) of ropivacaine 0.375% was injected. A successful block was obtained in all children. Excellent postoperative pain relief was obtained. All parents were satisfied with the postoperative pain relief. No complications occurred. CONCLUSION Ultrasonography is useful in the identification of the sciatic nerve and it facilitates needle and catheter placement for proximal and distal nerve blocks in children.

Detection of event-related desynchronization during attempted and imagined movements in tetraplegics for brain switch control

Motor-impaired individuals such as tetraplegics could benefit from Brain-Computer Interfaces with an intuitive control mechanism, for instance for the control of a neuroprosthesis. Whereas BCI studies in healthy users commonly focus on motor imagery, for the eventual target users, namely patients, attempted movements could potentially be a more promising alternative. In the current study, EEG frequency information was used for classification of both imagined and attempted movements in tetraplegics. Although overall classification rates were considerably lower for tetraplegics than for the control group, both imagined and attempted movement were detectable. Classification rates were significantly higher for the attempted movement condition, with a mean rate of 77%. These results suggest that attempted movement is an appropriate task for BCI control in long-term paralysis patients.

Towards a Novel Monitor of Intraoperative Awareness: Selecting Paradigm Settings for a Movement-Based Brain-Computer Interface

During 0.1–0.2% of operations with general anesthesia, patients become aware during surgery. Unfortunately, pharmacologically paralyzed patients cannot seek attention by moving. Their attempted movements may however induce detectable EEG changes over the motor cortex. Here, methods from the area of movement-based brain-computer interfacing are proposed as a novel direction in anesthesia monitoring. Optimal settings for development of such a paradigm are studied to allow for a clinically feasible system. A classifier was trained on recorded EEG data of ten healthy non-anesthetized participants executing 3-second movement tasks. Extensive analysis was performed on this data to obtain an optimal EEG channel set and optimal features for use in a movement detection paradigm. EEG during movement could be distinguished from EEG during non-movement with very high accuracy. After a short calibration session, an average classification rate of 92% was obtained using nine EEG channels over the motor cortex, combined movement and post-movement signals, a frequency resolution of 4 Hz and a frequency range of 8–24 Hz. Using Monte Carlo simulation and a simple decision making paradigm, this translated into a probability of 99% of true positive movement detection within the first two and a half minutes after movement onset. A very low mean false positive rate of <0.01% was obtained. The current results corroborate the feasibility of detecting movement-related EEG signals, bearing in mind the clinical demands for use during surgery. Based on these results further clinical testing can be initiated.

Detection of attempted movement from the EEG during neuromuscular block: proof of principle study in awake volunteers

Brain-Computer Interfaces (BCIs) have the potential to detect intraoperative awareness during general anaesthesia. Traditionally, BCI research is aimed at establishing or improving communication and control for patients with permanent paralysis. Patients experiencing intraoperative awareness also lack the means to communicate after administration of a neuromuscular blocker, but may attempt to move. This study evaluates the principle of detecting attempted movements from the electroencephalogram (EEG) during local temporary neuromuscular blockade. EEG was obtained from four healthy volunteers making 3-second hand movements, both before and after local administration of rocuronium in one isolated forearm. Using offline classification analysis we investigated whether the attempted movements the participants made during paralysis could be distinguished from the periods when they did not move or attempt to move. Attempted movement trials were correctly identified in 81 (68–94)% (mean (95% CI)) and 84 (74–93)% of the cases using 30 and 9 EEG channels, respectively. Similar accuracies were obtained when training the classifier on the participants’ actual movements. These results provide proof of the principle that a BCI can detect movement attempts during neuromuscular blockade. Based on this, in the future a BCI may serve as a communication channel between a patient under general anaesthesia and the anaesthesiologist.

The Episure Autodetect syringe, a loss-of-resistance technique for locating the epidural space, used in pediatric patients

The Episure Autodetect syringe, a spring‐loaded syringe, is a loss‐of‐resistance syringe with an internal compression that applies constant pressure on the plunger. As the principle of loss‐of‐resistance is the same for adult and for pediatric patients, the Episure Autodetect syringe should be able to identify correctly the epidural space also in pediatric patients.

Continuous Peripheral Nerve Blocks Safe Practice and Management

Continuous peripheral nerve blocks can be used to provide effective and prolonged analgesia. A variety of needle/catheter assemblies exist, and perineural catheters can be installed using various guidance mechanisms, including nerve stimulation and ultrasound. Complications that may hinder the efficacy of a continuous regional block include inaccurate catheter tip location, catheter dislocation, infection at the catheter insertion site, and difficulty removing the catheter. Neurologic injury with continuous blocks is rare and related to multiple risk factors. Other complications that affect single-injection blocks, such as accidental vascular puncture and systemic local anesthetic toxicity, may also occur with continuous blocks. Complications associated closely with continuous blocks include increased risk of patient falls and problems with the infusion regimen or equipment.

Proper training and use of ultrasonography facilitates lumbar puncture

With great interest, we read the study of Line Dussourd et al. concluding that ultrasonography allows better identification of anatomical structures before performing a lumbar puncture. We cannot concur with the conclusions of the study because the authors did not visualize the conus medullaris directly, nor did they assess the individual intervertebral levels. In our commentary, we make some suggestions for improvement using ultrasound to locate the optimal site for a lumbar puncture. We do agree that neuraxial ultrasound is of great benefit for the performance of lumbar punctures. Proper training and applying the correct technique, however, is necessary for obtaining all benefits ultrasonography offers.

Helping Children Cope With Medical Tests and Interventions

Medical procedures and tests become a challenge when anxiety and pain make it difficult for the patient to cooperate or remain still when needed. Fortunately a short intervention with hypnoidal language at the onset of a procedure induces a positive and sustained change in the way pain and anxiety are processed. While anesthesia may appear to be a simple solution to eliminate pain, the adverse effects of pre-anesthesia anxiety on postoperative behavior and recovery are often not fully appreciated. This paper discusses options for self-hypnotic relaxation that are applicable to interactions with children. The high suggestibility of children makes it relatively easy to engage them in make-believe scenarios. Avoidance of negative suggestions is key in avoiding nocebo effects that may be difficult to overcome later. Once a child is immersed in his or her preferred scenario or hobby/activity of choice, environmental and procedural stimuli can be easily integrated in the imagery. Ego-strengthening metaphors that tie in features of strength, confidence, or resilience are particularly empowering. Even when children are fully under general anesthesia they may still have recall of what is said in the room and therefore caution in word choice should be maintained.